Electric switching apparatus



March 19, 1957 J. 1 BEVINS 2,786,103

ELECTRIC SWITCHING APPARATUS Filed D80. 1, 1955 FIG. I

- 'INVENTOR. UMMES E. BEV/NS BYMMJM United States PatentfO ELECTRIC SWITCHING APPARATUS James E. Bevins, Ramsey, N. J., assignor to Bendix Aviation Corporation, Teterboro, N. J., a corporation of Delaware Application December 1, 1953, Serial No. 395,462

11 Claims. (Cl. 200-) This invention relates to electrical switching apparatus and particularly to rotary switching apparatus.

It is one object of the present invention to provide switching apparatus which will withstand wear due to constant use.

It is another object of the present invention to provide switching apparatus which will offer low friction drag so as to permit the use of minimum operating forces.

It is another object of the present invention to provide switching apparatus which may be confined to limited dimensions and yet be capable of withstanding high temperatures and high voltage gradients across the contacts when open without breakdown and to provide relatively long leakage current paths between the contacts when open.

It is still another object of the present invention to provide switching apparatus which is capable of maintaining electrical contact even though subjected to severe external vibrational influences.

it is a further object of the present invention to provide improved rotary switching apparatus providing double-throw type operation.

These and other objects, features and advantages of the present invention will be apparent from the following description of one embodiment considered in connection with the drawing wherein:

Fig. 1 is an isometric view partly in section of a rotary switch mechanism in accordance with the invention, the sizes of the various parts being exaggerated for pur-v poses of illustration; and

Fig. 2 shows one form of rotatable insulation member.

Turning to Fig. 1 there is indicated generally at a rotary switch providing eifectively single-pole, double throw operatiton for selectively applying either a 3-volt or 24-v0lt excitation to a load device indicated generally at 35.

Switch 10 includes a stationary ring-shaped base or support 11 composed of suitable electrical insulation material such as glass melamine. Secured to base 11 is a concentric metal terminal ring 12 of good electrical conductivity. Positioned in one slot in ring 12 is an electrical spring contact element 17 of good electrical conductivity and a block 15 of electrical insulation material which supports a second electrical spring contact element 16 similar to element 17. Contact elements 16 and 17 have their adjacent ends 24 bent towards each other to form lug portions embedded in block 15.

Positioned in another slot in ring 12 is a third electrical spring contact element 19 and an insulation block 15 which supports a fourth electrical spring contact element 18. Contact elements 18 and 19 are similar to elements 16 and 17 and may be secured to the associated insulation block 15 in the same manner. Two pairs of electrical insulation spacer members 13 and 14 are positioned on ring 12 in abutting relation on opposite sides of a respective insulation block 15. A slotted metal terminal block 25 is positioned on one pair of spacer members to receive contact element 16 and the associated 2,786,103 Patented Mar. 19, 1957 insulation block 15 in its slot. Similarly, a slotted metal terminal block 26 is positioned on the other pair of spacer members to receive contact element 18 and the associated insulation block 15 in its slot. Each terminal block and its associated spacer members, contact elements and insulation block are rigidly secured, by means (not shown) such as screws or bolts, to ring 12 and support 11. In this manner contact elements 17 and 19 are permanently held in good electrical contact with metal ring 12, contact element 16 is permanently held in good electrical contact with metal terminal block 25 and contact element 18 is held in good electrical contact with metal terminal block 26. Spacer members 13 and 14 serve to insulate the associated metal terminal block and its electrically common contact element from ring 12 and its electrically common contact elements 17 and 19. Contact elements 16 and 17 are identical in size and shape and are superposed one above the other. These elements are bent inwardly towards each other at their outer ends so that their respective portions 20 and 21 are urged into contact with each other along a line due to the inherent resiliency of elements 16 and 17. The tip ends of contact elements 16 and 17 are bent outwardly from each other beyond their line of contact. Contact elements 18 and 19 are constructed and arranged in the same manner as elements 16 and 17 except that elements 16 and 17 project closer to the central axis of rings 11 and 12 than do elements 18 and 19 as will be described hereinafter in greater detail.

A shaft 27 is positioned along the central axis of rings 11 and 12 for imparting input motion to switch it At the free end of shaft 27 is a hub member 29 which is rigidly secured to shaft 27, for example by means of a force-fit, solder or suitable threading. Hub 29 has two annular flange or lip portions 36 and 31. A thin glass cam disc 28 having a central aperture 28' is rigidly secured to hub 29 between the flange portions 30 and 31. Disc 28 is preferably composed of glass or other hard electrical insulation material such as mica or quartz which will not smear or rub off when passed into engagement with metal surfacessuch as the contact surfaces of elements 16-19.

. Cam edge AB is part of the circumference of an outer circle concentric about the central axis of rings 11 and 12 and extends for approximately Cam edges C-D and G-H are part of the circumference of an intermediate circle concentric about the central axis and extending for approximately 30 and respectively. Cam edge E-F is part of the circumference of an inner circle concentric about the central axis and extending for approximately 90. The cam disc and contact elements are arranged as shown in Fig. 1 so that upon rotation of shaft 27 and cam disc 28 through 360 the path of relative travel between contacts 18, 19 and disc 28 is represented by the outer dotted circle M and the path of relative travel between contacts 16, 17 and disc 28 is represented by the inner dotted circle N shown in Fig. 2.

By this arrangement one pair of contact elements are permitted to remain closed while the other pair of contacts are held open by disc 23, and vice versa. in Fig. l the intermediate cam edge (3-1) is shown displaced opposite contact elements 18, 19 and hence these contacts are permitted to remain closed while a. the same instant, a portion of disc 28 along the intermediate cam G-H is interposed between the contact portions at 2t), 21 of contact elements 16, 17 to hold these elements apart.

Assume now that the shaft and disc are angulariy displaced sufficiently so that point D of edge CD is located opposite the contact portions of elements 18, 19. Now if disc 28 is displaced through an angle of 240 in a counter-clockwise direction from this last-mentioned position, the contact portions of elements 1% and 19 will remain closed to maintain closed the associated circuit in which element 18 is connected, while during the same 240 of displacement disc 28 will remain inserted between the contact portions of elements i6, 17 to maintain open the associated circuit in which element 16 is connected.

If disc 23 is next displaced in a counter-clockwise direction through an additional angle of 90, the edge A-H will initially intercept the contact portions of elements 18, 19 and the portion of disc 23 bounded by edges I A, A-B and 3-0 will remain inserted between these contact portions during this 90 of displacement to open the associated circuit, while during this same 90 of displacement the inner edge .l3-F is passed opposite the contact portions of elements 16, i7 and out of contact therewith so that the latter contact portions are permitted to close the associated circuit. By providing contact elements for each pair of the contact elements illustrated in Fig. l which are symmetrical in size and shape, the contact portions of each pair will retain positive contact with each other when they are supposed to be closed even though the switch unit 11 is subjected to relatively severe vibrational influences. This prevention of contact chatter due to outside vibrational influences is made possible since the above-described arrangement of the pair or contact elements permits the elements of each pair to vibrate with the same amplitude and frequency.

One circuit arrangement with which switch 11 may be employed will now be described. A source (not shown) of A. C. voltage is connected across voltage supply terminals 3% and 31. Connected in parallel across terminals t: and 31 is an inductance 32 serving as a voltagedivider. Inductance 32 is provided with a 24-volt tap 33 and a 3-volt tap 34, these voltages being measured with respect to ground.

As previously stated, the metal ring 12 is permanently connected electrically in common with contact elements 17 and 19. Ring 12 is permanently connected in turn to the ungronnded side of a primary winding 36 of a rotatable transformer 35 which has a secondary winding 37 connected to a pair of output terminals 38 and 39.

Contact element 16 makes permanent electrical connection with metal terminal block which in turn is permanently connected to the 24-volt tap 33. Thus, closure of the contact portions of elements 16, 17 completes a circuit between the 24-volt tap and primary winding 36. Contact element 13 makes permanent electrical connection with metal terminal block 26 which in turn is permanently connected to the 3-volt tap 34. Thus, closure of the contact portions of contact elements 18,

19 completes a circuit between the 3-volt tap and primary winding 36. By the arrangement described a 3-volt excitation will be applied to primary winding 36 during 240 of counter-clockwise angular displacement of shaft 27 and disc 23, and during an additional 90 counterclockwise displacement of the shaft and disc a 24-volt excitation will be applied to primary Winding 36.

Although one embodiment of the invention has been illustrated and described in detail by way of example it is to be expressly understood that the invention is not limited thereto. Various changes may be made in the design and arrangement of the elements without departing from the spirit and scope of the invention as Will be understood by those skilled in the art.

I claim:

1. In electrical control apparatus, a pair of elongated generally parallel electrical spring contact elements, means for mounting said elements in fixed spaced relation at one end thereof, said elements having contact-making portions spaced from said one end and urged together by the resiliency of said elements, a member of electrical insulation material, and means including a shaft rigidly mounting said member for angularly displacing said member about the axis of said shaft, said member having a first peripheral portion adapted to remain out of engagement with said contact-making portions when said memher is angularly positioned anywhere in a first substantial range of angular positions, said member having a second peripheral portion adapted for insertion between said contact-making portions to interrupt electrical contact therebetween when said member is angularly positioned anywhere in a second substantial range of angular positions adjoining said first range, said first portion being augulariy ofi'set from said second portion and closer to said axis than said second portion to remain out of en agenrent with said contact-making portions for all ar positions of said member in said first and second ranges.

2. An electric rotary switch according to claim 1 wherein said rotatable member is composed of glass.

3. An electric rotary switch according to claim 1 wherein said rotatable member comprises a disc-like cam having its peripheral edge shaped to form said first and second portions.

4. An electric rotary switch according to claim 3 wherein said contact elements are substantially symmetrical in size' and shape and are mounted in opposed substantially co-cxtensive relations to each other, whereby said elements vibrate with the same amplitude and frequency to minimize discontinuity of contact when said switch is subjected to vibration.

5. Electric rotary switching apparatus comprising a first pair of stationary electrical contact arms urged into electrical contact, a second pair of stationary electrical contact arms urged into electrical contact, and a member of electrical insulation material rotatable through a first angular range to insert a portion of said member between the contact-making portions of said first pair of arms while the contact-making portions of said second pair of arms remain in engagement and rotatable through a difierent second angular range to insert a portion of said member between the contact-making portions of said second pair of arms while the contact-making portions of said first pair of arms remain in engagement.

6. Apparatus according to claim 5 wherein one contact arm of each of said pairs is connected permanently to a common electrical conductor, whereby said apparatus serves efiectively as a single-pole, double-throw switch.

7. In electrical control apparatus a first pair of stationary electrical spring contact elements urged into electrical contact, a second pair of stationary electrical spring contact elements urged into electrical contact, a member of electrical insulation material, and means including a shaft supporting said member for rotating said member through a first angular range to insert a first peripheral portion of said member between the contact-making portions of said first pair of elements while the contactmaking portions of said second pair of elements remain in engagement and for rotating said member through a difierent second angular range immediately following said first range to insert a second peripheral portion of said member between the contact-making portions of said second pair of elements while the contact-making portions of said first pair of elements remain in engagement.

8. An electric switch comprising a pair of relatively thin elongated generally parallel electrical contact arms having contact portions urged into contact-making engagement with each other, and relatively thin displaceable electrical insulation means having a thickness which is substantially uniform and which is of the same order of magnitude as the thickness of said contact arms, said insulation means having a portion displaceable to any one of a first series of successive rest positions for insertion between said contact portions and in engagement therewith to disengage said contact portions from electrical contact with each other while said insulation means is in any one of said rest positions, said portion of said insulation means being also displaceable to any one of another series of successive rest positions to permit contact-making engagement between said contact portions while said 5 insulation means is in any one of said other series of rest positions.

9. A switch according to claim 8 wherein said insulation means comprises a substantially flat glass disc.

10. An electric switch comprising a pair of stationary elongated generally parallel electrical spring contact elements having contact-making portions adapted to make electrical contact with each other due to the inherent resiliency of said elements, an angularly displaceable shaft, and an insulation member rigidly supported by said shaft for angular displacement therewith, said insulation member having a portion which remains out of engagement with said contact-making portions to permit engagement between said contact-making portions when said member is angularly positioned anywhere in a predetermined continuous substantial range of angular positions and which is inserted between said contact-making portions to disengage said contact-making portions when said member is angularly displaced to an angular position outside said range of positions.

11. An electric rotary switch comprising a pair of electrical spring contact arms having contact portions urged into electrical contact with each other, rotatable support means, and relatively thin electrical insulation means of substantially uniform thickness of the same order as the thickness of said contact arms, said insulation means being rigidly supported by said support means for rotation therewith and rotatable to any one of a series of different angular rest positions wherein a portion of said insulation means is interposed between said contact portions to break the contact therebetween for each such angular position and rotatable to another angular position wherein said portion of the insulation means is removed from between said contact arms to permit said arms to resume electrical contact.

References Cited in the file of this patent UNITED STATES PATENTS 393,183 Stocker Nov. 20, 1888 1,133,963 Hoover Mar. 30, 1915 1,273,245 Lundell July 23, 1918 1,999,695 Jackson Apr. 30, 1935 2,254,347 Blakesley Sept. 2, 1941 FOREIGN PATENTS 216,247 Switzerland Nov. 17, 1941 

